1. Field of the Invention
This invention relates to a composition and method for denaturing and breaking down friction-reducing polymer introduced into oil wells and for destroying other contaminants that are naturally present in and artificially supplied to oil wells as part of the oil drilling and pumping process.
2. Description of Related Art
Hydraulic fracturing is commonly used in oil well drilling applications. A typical conventional slick water fracturing protocol involves several hydraulic pumps that force a predetermined amount of water or more down-hole feed at a calculated rate and at a high pressure. The pressure of the water forced down-hole fractures the underground or subterranean rock formations thereby permitting gas and oil to flow freely into the well. Numerous chemicals are added on the fly as the water is forced into the well including but not limited to scale inhibitors, biocides, shale inhibitors, oxygen scavengers, friction-reducing agents, and flow-back additives. Friction-reducing agents are useful for decreasing the friction caused by the large volumes of water flowing through the hydraulic pumps. Friction-reducing agents also reduce the pressure placed upon the hydraulic pumps. Flow-back additives, such as the present inventive composition, assist friction-reducing agents at the beginning of a fracturing job by decreasing friction and also assist in breaking down or dissolving the friction-reducing agent after the fracturing job is completed.
Fracturing chemicals, fracturing sand, and water are pumped down-hole into a well under high pressure to fracture the subterranean formation during a fracturing job. The fractures in the subterranean formation created by the fracturing fluid and water under pressure are held open by the fracturing sand. Once this fracturing process is complete, oil and gas flow into the wellbore through the fractures and the flowback of the friction-reducing polymer begins. The pressure of the subterranean formation pushes the fracturing fluid out of the well into tanks above ground. Depending upon the depth of the well and the amount of fracturing fluid used, the flowback can continue for a period lasting from several days to approximately one month. When the flowback ends, most of the fracturing fluid including the friction-reducing polymer has been removed and the oil well is ready for production.
U.S. Pat. No. 5,031,700, issued to McDougall et al., on Jul. 16, 1991, describes a method of improving the permeability of subterranean formations, and particularly the permeability of sandstone formations containing clays and silicates, using chlorine dioxide. The '700 patent does not describe the use of an oxy-chloro compound for denaturing and breaking down or decomposing friction-reducing polymer and other toxic chemical and biological agents and organisms.
U.S. Pat. No. 4,945,992, issued to Sacco on Aug. 7, 1990, describes a process for producing as well as for cleaning high pressure water injection wells and oil-producing wells. The '992 patent does not describe the use of an oxy-chloro compound for denaturing and breaking down or decomposing friction-reducing polymer in an oil well.
U.S. Pat. No. 4,871,022, issued to McGlathery on Oct. 3, 1989, describes a method for removing polymer plugging material from injection and oil-producing wells. The '022 patent does not describe the use of an oxy-chloro compound for denaturing and breaking down or decomposing friction-reducing polymer in an oil well, but describes a method for removing polymeric material from the well that was added in the form of an aqueous flooding medium to dislodge oil present in formation solids. Once dislodging the oil from these formations, the aqueous polymeric flooding medium of the '022 patent forces the oil toward a primary well bore for recovery. However, over time, the polymeric medium forms a polymer plug by leaving solid polymeric deposits on the walls of the well bore and interstices of the perforated zone of the formation.
U.S. Pat. No. 4,964,466, issued to Williams et al., on Oct. 23, 1990, describes a method of fracturing a subterranean formation using hydraulic fracturing with chlorine dioxide for cleanup. The '466 patent does not describe the use of an oxy-chloro compound for denaturing and breaking down or decomposing friction-reducing polymer, scale inhibitors, biocides, shale inhibitors, oxygen scavengers, friction-reducing agents, and flow-back additives in an oil well. Moreover, the present invention effectively uses oxy-chloro compounds at much lower levels (for example, 0.40 to 10.0 ppm (parts per million)) than the '466 invention.